A tire valve usually has a valve stem with a valve that extends through a stem hole in a wheel rim. The inner volume of the valve stem is in fluid communication with the hollow chamber enclosed by the tire. The valve in the stem permits air to be introduced into the tire and prevents escape of the air from the tire through the valve stem. The valve stem may be rubber or a rigid, metal stem, and is usually provided with a removable valve cap or dust cap on its threaded end. The cap is used to protect the inside of the valve.
Even though a rubber valve stem may be resilient, so that it may be sealed in the wheel rim opening as the stem is pulled into place, the rubber is exposed to various sharp objects with which it may come into contact while driving. Also, the rubber valve stem may become brittle or deteriorate due to exposure to the sun and contact with various salts, oils and other road-related substances.
A tire valve is very important for maintaining the correct air pressure in a tire. It is important for safety reasons but also for achieving optimal fuel efficiency and maximizing tire life. Under-inflated tires may result in rapid and excessive wear on the outer portions of the tread as well as improper vehicle handling. On the other hand, over-inflated tires may result in rapid and excessive wear on the middle part of the tread, and may possibly lead to a blowout.
Devices for checking or monitoring tire pressure have been available for many decades. The most common method for monitoring tire pressure is manual measurement using a tire gauge. This involves removing the valve cap and applying the tire gauge to the valve stem. Firstly, this method is complicated and requires an additional tool, which may be unavailable when needed and must be purchased at an additional cost to the operator. Secondly, the operation is time consuming for the operator as he must remove the valve cap for each tire, apply the pressure gauge, and then re-fasten all the valve caps. For recreational vehicles and trucks, or other vehicles with generally more wheels, this task can be onerous.
Another example of known tire pressure detection is the use of a tire pressure sensor installed on the inflation valve. However, when inflation or deflation of the tire is required, the tire pressure sensor has to be removed, which is still inconvenient and time consuming. Furthermore, it may be more time consuming because such pressure sensors are often fitted with a locking mechanism that needs to be undone and re-done. Such sensors, when detached while adjusting the tire pressure, may be lost in the same way that valves caps are often lost or forgotten. This is more of a problem due to the greater expense of the pressure sensors.
Other examples of prior art for tire pressure detection are disclosed in U.S. Pat. No. 1,176,907 and US Patent Application Publication No. 2008/0149244, both of which describe an adapter which is screwed onto the valve stem and which has two branches. On one branch, the pressure sensor is mounted, while the other branch may be used to relieve pressure or to pump air into the tire. However, as the disclosed valves and pressure detectors are not an integral part of the tire valve, the whole assembly becomes cumbersome and too weighty, affecting a wheel's balance. If the adapter and sensor are attached to a rubber valve stem, centripetal forces due to wheel rotation cause the rubber stem to deform while driving, which may lead to damage of the stem, deflation of the tire and a possible accident. A further problem with the use of an adaptor is that its use introduces at least one more joint through which air or contaminants may leak.
Accordingly, there is a need for a less cumbersome solution that permits the adjustment of air pressure without the need to remove a pressure sensor.
The foregoing examples of the prior art and the limitations related thereto are intended to be illustrative only and not exclusive. Other limitations of the prior art will become apparent upon reading the specification and study of the drawings.